The piezoelectric effect is a phenomenon of energy conversion between mechanical energy and electrical energy within certain materials such as piezoelectric ceramics as a common piezoelectric material which possesses excellent piezoelectric performance such that it is widely used in various piezoelectric devices, e.g., ultrasonic oscillator, ultrasonic motor, piezoelectric transformer and filters.
An ultrasonic oscillator can be applied to in technical fields including cleaning, emulsification and welding. In ultrasonic cleaning, it utilizes an element made of piezoelectric ceramics to oscillate in liquid at ultrasonic frequency of tens of thousands times per second such that the liquid is agitated to produce numerous cavitation bubbles which implode and release energy in such a manner that it performs cleansing action by penetrating and reaching the insides of deep slits and cracks to remove contaminants thereon, thereby obtaining a good cleaning effect. In ultrasonic emulsification, high frequency voltage signals are generated by electric circuits, then electric energy is converted into mechanical energy by transducers, and at last immiscible liquids are emulsified to form an emulsion. In ultrasonic welding, the area of a workpiece is contacted to be welded together by applying a welding head which exerts ultrasonic vibrations to the parts to be welded.
The basic structure of conventional ultrasonic oscillators (i.e. piezoelectric oscillator device) includes a cylindrical body which can be hollow or solid, and one end of the cylindrical body is connected to a piezoelectric device or both ends of the cylindrical body are respectively connected to two piezoelectric devices as a source for transmitting acoustic waves. When powered on, the piezoelectric device generates ultrasonic vibrations which travel through the cylindrical body. However, excessively strong acoustic waves and prolonged impact and oscillation may cause the ultrasonic oscillator to be damaged. As mentioned above, it is necessary to improve the conventional piezoelectric oscillating device.